Firing rate regulator for a gas-operated firearm

ABSTRACT

A firing rate regulator for an automatic firearm having a breech mechanism operated by gas pressure. A breech casing has a gas channel and a throttling element is responsive to a temperature change for regulating the gas pressure by varying the cross sectional area of gas flow through the gas channel. Members made of materials having different coefficients of thermal expansion move the throttling member. The throttling element may be a piston with an annular groove movable in the casing and biased on one side by a spring and on the other side by a liquid such as mercury whereby the position of a flank of the groove determines the cross sectional area of the gas channel or a rotatable pin projecting into the gas channel with a bimetal spring for rotating the pin to vary the cross sectional area of the gas channel.

United States Patent Muhlemann [451 Aug. 1, 1972 [72] Inventor: ErnstMuhlemann, Zurich, Switzerland [73] Assignee: WerkzeugmaschinenfabrikDerlikon- Buhrle AG, Zurich, Switzerland 22 Filed: July 8,1970

21 Appl. No.: 53,256

[30] Foreign Application Priority Data July ll, 1969 Switzerland..106l6/69 [52] US. Cl. ..89/193 [51] Int. Cl ..F4ld 5/08 [58] Field ofSearch ..89/191, 192, 193

[56] References Cited UNITED STATES PATENTS 2,918,848 12/1959 Maillard..89/193 1,738,501 12/1929 Moore ..89/193 1,387,889 8/1921 Johnston..89/193 Primary Examiner-Stephen C. Bentley Attorney-Wenderoth, Lindand Ponack [5 7 ABSTRACT A firing rate regulator for an automaticfirearm having a breech mechanism operated by gas pressure. A breechcasing has a gas channel and a throttling element is responsive to atemperature change for regulating the gas pressure by varying the crosssectional area of gas flow through the gas channel. Members made ofmaterials having different coefficients of thermal expansion move thethrottling member. The throttling element may be a piston with anannular groove movable in the casing and biased on one side by a springand on the other side by a liquid such as mercury whereby the positionof a flank of the groove determines the cross sectional area of the gaschannel or a rotatable pin projecting into the gas channel with abimetal spring for rotating the pin to vary the cross sectional area ofthe gas channel.

5 Claims, 12 Drawing Figures PATENTED H 3,680,434

' sum 1 or a V3 36 40433 A I ERNST MUHLEMANN, Inventor AttorneysPATENTEDA B 1 I97? 3,680,434

SHEET 2 [1F 4 ERNST MUHLEMANN, Invent-.3:

Attorneys PATENTEDAW 1 1912 3,680,434

sum 3 or 4 ERNST MUHLEMANN, Inventor BymmmimMM Attorneys PATENTEDAus 1I972 3.680.434 susnmnrd ERNST MUHLEMANN, Inventor At torncys FIRING RATEREGULATGR FGR A GAS- OPERATED WARM The invention relates to a firingrate regulator for a gas-operated firearm of the type comprising athrottling element which in response to temperature controls the gaspressure for operating a breech mechanism of the firearm by varying thecross sectional area of flow through a gas channel.

A known form of rate regulator of this type consists of a pin inside acylinder. An annular cross section of flow for the gases remains betweenthe pin and the cylinder. The pin as well as the cylinder are made ofsteel. When the weapon is fired the pin which is immersed in the flowinggas becomes hotter more quickly than the greater mass of the cylinder.The pin therefore initially expands more rapidly than the cylinder andthe annular cross section of flow is reduced, throttling the passage ofthe gas. This effect compensates the tendency of the firearm to increaseits firing rate.

This known type of firing rate regulator has the de feet that in thecourse of a prolonged burst of firing the temperature difference betweenthe pin and the cylinder gradually entirely vanishes and that the rateregulator then ceases to exercise any control.

It is the object of the present invention to eliminate this defect.

A firing rate regulator according to the invention for a gas-operatedfirearm comprises a throttling element which in response to atemperature change regulates the gas pressure for operating a breechmechanism of the firearm by varying the cross sectional area of flowthrough a gas channel, and means for moving the throttling elementcomprising members made of materials having different coefficients ofthermal expansion.

The invention is illustrated by way of example in the drawings of which:

FIG. 1 is a section of the barrel of a firearm having a firing rateregulator according to the invention;

FIG. 1a is an enlarged representation of part of FIG.

FIGS. 2 to S are sections taken on the lines II-II, III-III, [VIV and VVof FIG. la;

FIG. 6 is a sectional view of an alternative part of FIG. 1 for use inthe regulator of FIGS. l to FIG. 7 is a section of an alternativeembodiment of a firing rate regulator according to the invention;

FIG. 8 is a view in the direction of the arrow A in FIG. 7;

FIG. 9 is a view in the direction of the arrow B in FIG. 8;

FIG. 10 is a section of a further embodiment of a firing rate regulatoraccording to the invention and FIG. 1 1 is a view similar to that ofFIG. 9 of the regulator of FIG. 10.

With reference to FIGS. 1 and la the barrel ll of an automatic firearmis held fast in a breech casing 2. The breech casing 2 includes acylindrical chamber 3 in communication with the interior of the barrel 1through a gas passage 4. The chamber 3 is closed by a plug 5, andcontains a slidably movable piston 6 attached to a piston rod 7. Therear end of the piston rod 7 projects through the rear end of thechamber 3 and abuts onto a sleeve 8 which is biased by a spring 9. Inthe illustrated position of the piston 6, the head of the piston bearsagainst an end face 10 of the plug 5. The chamber 3 also contains astack of annular springs ll which form a bufier for the piston 6 bycooperating with an annular face 12 on the back of the piston head. Abore 13 in the wall of the chamber 3 connects the chamber interior withthe ambient atmosphere.

The bore of the chamber 3 at its forward end 14 has a larger diameterthan its rear part 15. The two diameters l4! and 15 are separated by ashoulder 16. The diameter of a rear portion 17 of the plug 5 equals thatof the chamber bore 15 into which it projects. The diameter of a frontportion 18 equals the diameter of the chamber bore 14. An annularshoulder 19 separates the portions l7, 18 of the plug 5. An annularchamber 20 is formed between the shoulders 16 and I9. Adjacent to theannular chamber 20 the rear portion of the plug is provided on itscircumference with an annular groove 21. A second annular groove 76 ismachined into the rear portion of the plug 5. The gas passage 4communicates with the annular groove 76. The two annular grooves 21, 76communicate through a helical groove 75 cut into the circumferentialsurface of the rear portion of the plug 5. The front annular groove 21communicates through four radial ducts 22 (FIG. 2) with a blind axialbore 23 in the plug 5. The bore 23 is open at the end face It) of theplug and is coaxial with the axis of the cylindrical chamber 3.

The plug 5 projects from the forward end 114 of the chamber 3 where itis formed with a flange 24 which abuts a face 25 of a shoulder at thefront end of the chamber 3. A blind bore 26 is drilled through the plug5 from its front end axially aligned with the axis of the chamber 3. Twogrooves 27 and 28 which extend around the entire internal circumferenceof the bore 26 are machined into its internal wall. Milled atequidistant intervals into the circumferential surface (FIG. 3) ofportion 118 of the plug 5 are four grooves 29 which communicate with theannular chamber 20 and which are axially parallel to the chamber axis.Four radial bores 30 connect the grooves 29 to the groove 28. A numberof ducts 31 extend from the groove 27 to an annular face 32 of theflange 24 of the plug 5. A cylindrical container 33 is inserted into thebore 26 of the plug 5 and threadedly located therein. The rear portionof the container 33 has a central bore 34. A groove 35 machined into thewall of the bore 34 contains an O-ring 36. The container 33 encloses acavity 33 which is completely filled with mercury. Mercury has a muchhigher coefficient of thermal expansion than the steel of which thecontainer 33 and the plug 5 are made. A plunger 37 is movable inside thebore 34 and projects into the container 33. A stack of Bellevillesprings 39 bears against a rear face 47 of the bore 26 of the plug 5.The bore 26 contains a piston 40 whose position is controlled by theBelleville springs 39, and by the plunger 37 which projects from a rearface 42 of the container 33. End faces 44 of the piston 40 each containtwo intersecting diarnetrical grooves 413 which are perpendicular toeach other. The grooves 43 are shorter than the diameter of the piston40 and longer than the diameter of the plunger 37. The grooves 43 inboth end faces all are interconnected by a central bore 44. Machinedinto the piston 40 is an annular groove 45 which is sufficiently widefor its rear flank 46 to come below the groove 28 when the piston 40 isdisplaced, and thus to establish communication between the groove 28 andthe groove 27. The described rate regulator functions as follows:

Before firing begins, when the firearm to still cold, the piston 40completely covers the groove 28 in the plug 5 as shown in FIG. 1a.Moreover, the groove 45 in the piston 40 is located so as to be incommunication with the groove 27 in the plug 5. In the course of firinga round (not shown) powder gases pass from the barrel into the gaspassage 4. The powder gases will pass through this passage and enter therear annular groove 76, thence flowing along the helical groove 75 intothe front annular groove 21 and into the annular chamber 20. From herethe gas flows through ducts 22 and 23 to the face of the piston 6 andits pressure accelerates the piston and piston rod to the rear thusoperating the breech mechanism of the automatic firearm in a knownmanner. The front end of the piston 6 when it reaches the end of itsstroke, will have uncovered the bore 13 permitting the gas to escapefrom the chamber 3 to atmosphere. The annular face 12 of the pistonstrikes the stack of springs 11 which decelerate the piston and cause itto rebound towards the plug 5 with which it remains in contact-until thenext round is fired.

As the gun continues to fire the barrel 1 is heated up by the powdergases, and this heat is transmitted through the chamber 3 to the plug 5enclosing the container 33 and to the mercury confined in the cavity 38and all these parts 3, 5, 33, 38 therefore likewise become hot. Thisrise in temperature causes the mercury to expand more than the container33 and the plug 5. Expansion of the mercury displaces the plunger 37 andthe piston 40 to a distance dependent on the tempera ture of the barrel,against the resistance of the Belleville springs 39. The rear flank 46of the annular groove 45 of the piston 40 is thus displaced rearwards soas to be in communication with the groove 28 of the plug 5. A proportionof the gas diverted from the barrel 1 through the gas passage 4 afterthe firing of each round will therefore now escape from the annularchamber through the grooves 29 and the bores 30 into the groove 28 andfrom there into the groove 45, the groove 27 and via the ducts 31 toatmosphere. Consequently less gas pressure is available for displacingthe piston 6 which is less powerfully accelerated and therefore delaysthe unlocking of the breech mechanism, (not shown) until the gaspressure in the barrel 1 has fallen to a lower level. The lower residualgas pressure transmits less power to the breech mechanism whichtherefore moves more slowly and reduces the firing rate which hadincreased by virtue of the firearm having become hotter.

During the displacement of the piston 40 the pressures equalize throughthe bore 44 and the grooves 43 in the piston 40 between the rear end andthe chamber in front of piston 40 defined by its end face 41 and the endface 42 of the container 43. When after the termination of firing theplug 5 and the container 33 cool off the plunger 37 and the piston 40are restored to their initial position by the thrust of the Bellevillesprings 39. The biasing force of the springs 39 is sufficient to ensurethat the frictional resistance to motion affecting the plunger 37 andthe piston 40 due to carbon deposits on the wall of the bore 26 or dueto the sealing ring 36 are overcome.

During the period before the above-described thermal gas regulation hasnot yet become effective, an increase in the firing rate is resisted dueto the design of the gas channels in the rear portion 15 of the plug 5.

The gas channels comprising the passage 4, the annular grooves 21, 76,the helical groove 75 and the bores 22, 23 cause a drop in pressure ofthe gases passing through them. This pressure drop is due to a loweringin pressure incurred in the gas channels by friction and turbulence ofthe gas. These pressure losses are accentuated by the length of the gaschannel and by angles in its path, and they become more pronounced asthe gas temperature and consequently the gas velocity rises so that thedesign of the entire system of channels already operates to resist arise in the firing rate.

FIG. 6 illustrates an alternative form of container for use with thedescribed regulator. As shown in FIG. 6 the bore 26 of the plug 5contains a flexible resilient corrugated tube 49 which is closed at oneend by a cover 50 that screws into the plug 5 and at the other end by abase 51 abutting against the piston 40. The rate regulator functionssubstantially in the same way as that described with reference to thefirst embodiment. The mercury enclosed in the container 48 expands at ahigher rate than the plug 5 when both become hot and therefore displacesthe piston 40 to the rear. The corrugated tube 49 is elasticallyelongated by the thrust of the mercury on the base 51.

With reference to FIGS. 7 to 9 the barrel 1 is attached to a breechcasing 52 which contains a forwardly open cylinder 53. A sleeve-shapedextension of an insert 54 projects into the open end cylinder 53 and isthreadedly connected thereto. The cylinder 53 and the extension 55together define a cylindrical chamber 56 in which a piston 57 isslidably movable. In its position of rest the piston 57 is biased by aspring 59 acting on its piston rod 58 against a bottom 60 of the bore ofthe extension 55. A gas passage 61 passing from the interior of thebarrel 1 communicates with a bore 62 in the insertion 54. The bore 62 isconnected to a blind bore 63 which is coaxial with the sleeve shapedextension 55 and communicates with the interior of the cylinder chamber56. The bore 62 ends at the upper face 65 of the insertion 54. The partof the bore 62 between the junction of the blind bore 63 and the bore 62and the upper face 65 of the insertion 54 forms a venting channel 64. Abore 66 penetrates the insertion 54, its axis perpendicularlyintersecting the axis of the venting channel 64. This bore 66 has alarger diameter than the venting channel 64. A pin 67 is rotatablymounted in the bore 66. Machined into the ends of the pin 67 whichproject from both sides of the insertion 54 are grooves 68 which havecoincident axes of symmetry and contain the axis of the pin 67. The pin67 contains a slot 69 of a width equal to the diameter of the bore 64and bounded by an edge 73. The plan of symmetry of the slot 69 is normalto the axis of the venting channel 64 and also contains the axis of thebore 66. Attached to each side of the insertion 54 are holders 7%). Eachholder 70 grips the ends of two metal strips 71a, 71b having differentcoefficients of thermal expansion of a bimetal spring 71. The other endsof the metal strips 71a, 71b of the bimetal spring 71 are rivetedtogether at 72 and project into the slots 68 of the pin 67. Rivets 72having round heads contact the walls of the slots 68 at points which arecoplanar. This plane is normal to the plane of symmetry of the slot 68and is offset from the axis of rotation of the pin 67.

This embodiment described above functions as follows. In the position ofrest of the pin 67 which is shown in FIG. 7 the venting channel 64 isclosed. The insertion 54 is heated by the gas diverted from the barrelduring firing through the bores 61, 62, 63 to the piston 57 as well asby thermal conduction and radiation from the barrel 1. The temperatureof the two bimetal springs 71 is raised by heat radiated through theinsertion 54 and through the barrel 1. Owing to the differentcoefficient of thermal expansion of the metals of the strips 71a, 7 lbof the bimetal springs 71 the latter flex and their ends apply aclockwise torque to the pin 67 (as viewed in FIG. 9). Rotation of thepin 67 brings the edge 73 bounding the slot 69 in the pin 67 into theventing channel 64, thereby permitting some of the gas entering throughthe channel 62 to escape through the venting channel 64, the slot 69 inthe pin 67 and the upper part of the venting channel 64. Consequentlyless gas will flow to the piston 57 and the firing rate of the firearmwill slow down in the same way as described in connection with the firstembodiment.

FIGS. 10 and 11 illustrate a further embodiment which merely differsfrom the embodiment of FIGS. 7 to 9 in that the gas channel 61, 62, 63does not communicate with the ambient atmosphere. The bore 62 in thisarrangement merely extends as far as the blind bore 63. The pin 67crosses the bore 62, and the holders 70 for the bimetal springs 71 areattached to the upper end of the insertion 54. The pin 67 contains abore 74 which in the position of rest shown in FIG. 10 is coaxiallyaligned with the bore 62 and which has the same diameter as the latter.Owing to the rotation of the pin 67 when the bimetal springs 71 becomehot, the cross section of flow of the bore 62 is reduced and the gassupply to the piston 57 is throttled with a consequent reduction in thefiring rate of the gun.

In the two embodiments illustrated in FIGS. 7 to 11 the pin 67 isrotated back into its former position when the gun cools by virtue ofthe bimetal springs 71 likewise becoming cooler.

I claim:

1. A firing rate regulator for an automatic firearm having a breechmechanism operated by gas pressure comprising a breech casing having agas channel, a throttling element in said casing responsive to atemperature change for regulating said gas pressure by varying the crosssectional area of gas flow through said gas channel, said casing havinga bore, said throttling element comprising a piston having an annulargroove movable in said bore, a spring biassing said piston on one sideand a liquid on the other side, whereby the position of a flank of saidgroove determines the cross sectional area of said gas channel, saidcasing and said liquid having different coefficients of thermalexpans1on.

2. A firing rate regulator for an automatic firearm having a breechmechanism operated by gas pressure comprising a breech casing having agas channel, a throttling element in said casing responsive to atemperature change for regulating said gas pressure by varying the crosssectional area of gas flow through said gas channel, said throttlingelement comprising a rotatable pin projecting into said gas channel, anda bimetallic spring for rotating said pin to vary the cross e ti f s 'dban 1. s %%r i rfg ate reg l a%or a gording the claim 1, in

which said liquid is mercury.

4. A firing rate regulator according to claim 1, wherein said casing hasa port venting to the atmosphere and the position of said flankdetermines the cross sectional area of flow between a part of said gaschannel and said port.

5. A firing rate regulator according to claim 2, in which said pinprojects into a venting channel which connects said gas channel toatmosphere and a rise in temperature actuates said pin to be moved toincrease the cross sectional area of said venting channel.

1. A firing rate regulator for an automatic firearm having a breechmechanism operated by gas pressure comprising a breech casing having agas channel, a throttling element in said casing responsive to atemperature change for regulating said gas pressure by varying the crosssectional area of gas flow through said gas channel, said casing havinga bore, said throttling element comprising a piston having an annulargroove movable in said bore, a spring biassing said piston on one sideand a liquid on the other side, whereby the position of a flank of saidgroove determines the cross sectional area of said gas channel, saidcasing and said liquid having different coefficients of thermalexpansion.
 2. A firing rate regulator for an automatic firearm having abreech mechanism operated by gas pressure comprising a breech casinghaving a gas channel, a throttling element in said casing responsive toa temperature change for regulating said gas pressure by varying thecross sectional area of gas flow through said gas channel, saidthrottling element comprising a rotatable pin projecting into said gaschannel, and a bimetallic spring for rotating said pin to vary the crosssectional area of said gas channel.
 3. A firing rate regulator accordingthe claim 1, in which said liquid is mercury.
 4. A firing rate regulatoraccording to claim 1, wherein said casing has a port venting to theatmosphere and the position of said flank determines the cross sectionalarea of flow between a part of said gas channel and said port.
 5. Afiring rate regulator according to claim 2, in which said pin projectsinto a venting channel which connects said gas channel to atmosphere anda rise in temperature actuates said pin to be moved to increase thecross sectional area of said venting channel.